[Paleopsych] NYTBR: 'Warped Passages': The Secret Universe
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Mon Oct 24 22:29:42 UTC 2005
'Warped Passages': The Secret Universe
Unraveling the Mysteries of the Universe's Hidden Dimensions.
By Lisa Randall.
Illustrated. 500 pp. Ecco/HarperCollins Publishers. $27.95.
By TIM FOLGER
IN 1900, the British physicist Lord Kelvin assured a gathering of his
colleagues, "There is nothing new to be discovered in physics now."
What a difference a century makes. Physicists today are all too aware
of the holes in their theories. Lordly smugness isn't an option, not
when physicists readily concede that more than 95 percent of the mass
of the universe apparently consists of an unknown substance that,
lacking any better description, they simply call dark matter. And just
a few years ago astronomers discovered that the expansion of the
cosmos is accelerating, driven by who knows what. Most vexing of all,
physicists know that the two masterpieces of their discipline, quantum
mechanics and general relativity, are incompatible and cannot in
themselves be the final word on the nature of reality.
Lisa Randall's chronicle of physicists' latest efforts to make sense
of a universe that gets stranger with every new discovery makes for
mind-bending reading. In "Warped Passages," she gives an engaging and
remarkably clear account of how the existence of dimensions beyond the
familiar three (or four, if you include time) may resolve a host of
cosmic quandaries. The discovery of extra dimensions - and Randall
believes there's at least a fair chance that evidence for them might
be found within the next few years - would utterly transform our view
of the universe.
Randall, a theoretical physicist at Harvard, writes from the trenches:
she's been working on higher-dimensional models of the universe for
several years now. Her work is a departure from mainstream physics, in
particular from string theory, which has its own take on extra
According to string theory, the most fundamental constituents of
matter and energy are not particles, but infinitesimally small strings
and loops that vibrate in 10 dimensions. The extra dimensions, string
theorists contend, are so small and tightly curled that they are
beyond the reach of any conceivable particle accelerator. Many
physicists are willing to overlook the lack of experimental evidence
because they believe that string theory will eventually reconcile
quantum mechanics, which governs atoms and all other particles, with
general relativity, which describes how matter and gravity interact on
the very largest scales.
Randall, though, argues that without any experimental feedback, string
theorists may never reach their goal. She prefers a different
strategy, called model building. Rather than seeking to create an
all-encompassing theory, she develops models - mini-theories that
target specific testable problems and that might then point the way to
a more general theory.
The models that Randall and her collaborator Raman Sundrum have been
building may explain one of the greatest mysteries in physics: why is
gravity so weak compared with the other forces in the universe?
Gravity's weakness may not seem obvious, but as Randall writes, "A
tiny magnet can lift a paper clip, even though all the mass of the
earth is pulling it in the opposite direction." The electromagnetic
force is a trillion trillion trillion times as powerful as gravity.
To account for gravity's feebleness, Randall and Sundrum borrow some
ideas from string theory but add their own twist. What if, they ask,
higher dimensions are not small and curled up but large, perhaps
infinite in size? Would there be any observable consequences? So they
build models of what the universe might look like if it consisted of
objects called branes (short for "membranes"). Branes, a creation of
string theory, are surfaces that exist in higher-dimensional space. In
Randall and Sundrum's various models, our universe is a
four-dimensional brane (three dimensions of space and one of time)
that exists on the surface of a five-dimensional space, much as a
two-dimensional layer of water covers a three-dimensional sea.
Their models, it turns out, produce a weakened gravitational force.
But most important, they predict the existence of particles that may
be detectable when a giant new particle accelerator called the Large
Hadron Collider, under construction near Geneva, begins smashing
protons together in 2007. The expectation is that the collider will
discover a group of new particles, and perhaps even miniature black
holes. If Randall and Sundrum's predictions pan out, and the existence
of extra dimensions is confirmed, it would be one of the biggest
advances in physics in decades.
To set the stage for all this, Randall has to recap nearly a century
of physics, which she accomplishes with extraordinary clarity. Her
explanation of the uncertainty principle, a central tenet of quantum
mechanics, is the best I have ever read. Along the way she includes
some surprising historical sidelights. Dalí's "Crucifixion," she
points out, depicts a four-dimensional cube. The full lyrics of "As
Time Goes By" include a reference to Einstein and the fourth
dimension. Einstein's calculus teacher, Hermann Minkowski, called his
most famous pupil a "lazy dog." And Randall's perspective as a woman
in a field where men hold 90 percent of all faculty positions makes
for some wry comments. I doubt it would occur to most physicists to
observe, "If, however, you lived inside a black hole, your travel
opportunities would be far more severely constrained, more restricted
even than those of women in Saudi Arabia."
Some of her devices are a bit silly - for example, she opens each
chapter with the adventures of time-and-interbranal-traveling
characters named Athena and Ike Rushmore. Perhaps it's an occupational
hazard: physicists who write for the general public often seem not to
trust their own material. But a little silliness in a book that's
freighted with discussions of gauge bosons, supersymmetry and D-branes
is not necessarily a bad thing. In any case, none of her words are
sillier than Lord Kelvin's.
Tim Folger is a contributing editor at Discover magazine and the
series editor for "The Best American Science and Nature Writing," an
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